Magnetic composition and method of making same.



Uuirnn STATES Patented December 1, 1903.

PATENT OFFICE.

MAGNETIC GOMPOSlTION AND METHOD OF MAKING SAME.

SPECZFIGATION forming part of Letters Patent No. 745,829, dated December1, 1903.

Application filed Tune 12, 1903. Serial No. 161,228. (No s e imens.)

To all whom it may concern.-

Be it known that 1, ROBERT ABBOTT HAD- FIELD, a subject of the King ofGreat Britain, and a resident of Sheffield, county of York, England,have invented certain new and useful Improvements in MagneticCompositions and Methods of Making the Same, of which the following is aspecification.

My invention relates to material having magnetic and electricalproperties suitable for use in various electrical apparatus, such asballast-coils, transformer-plates, and the like.

The object of my invention is to produce an improved material of thischaracter having specially high permeability and electrical resistanceand low hysteresis qualities. I have found that material of thesedesirable qualities can be produced by alloying iron with otherelements, among which I will name silicon and aluminium, phosphorus alsoyielding satisfactory results, as well as combinations of two or threeof these elements.

I may proceed, for instance, as follows: I take pure Swedish or othersuitable pure iron and melt this is a common crucible or electricallyalong with silicon or aluminium or phosphorus, employing a percentage ofthese additions varying from one-quarter of one per cent. to five percent. As above stated, I may employ only one of the three elementsmentioned or two of them, or all three. Instead of the crucible processI may employ the decarbonized or desiliconized iron produced by anysteel-making process-such as the open-hearth, the pneumatic, or theelectrical processadding to such iron the desired percentage of silicon,aluminium, or phosphorus. The molten alloy is poured into suitableingots, which are, if desired, forged or rolled into the desired shape.

As an example of the exact composition of alloy produced I will refer toone actually manufactured by me, which contained 2.75 per cent. silicon,.07 per cent. carbon, .08 per cent. manganese, .03 per cent. sulfur, .03per cent. phosphorus.

The material produced as above described is valuable on account of itshigh magnetic permeability, its high electrical resistance,

and low hysteresis for efficient use in transformers and otherelectrical apparatus in which said qualities are useful.

I have found that the superior qualities of my improved material ofalloy can be still further enhanced by a treatment involving alternateheating and cooling and generally carried out as follows: I first heatthe material to between about 900 and 1,100 centigrade and allow it tocool, preferably quickly. Then I reheat the material to between about700 and 850 centigradethatis,to a temperature lower than the oneattained during the first heatingand then allow the metal to cool veryslowly. In practice the cooling has been often extended to last severaldays. Either one or both of these treatments may be frequently repeated,or after the first treatment has been carried out the second type ofheating may be frequently repeated. I have, for instance, taken a steelalloy of the'composition above mentioned, heated it to 1,070 Centigrade,cooled it quickly to atmospheric temperature, reheated it to 750centigrade, cooled slowly, again reheated to 800 centigrade, and againcooled slowly. I have found that when the best results are desired it isof great importance to use the exact temperatures that correspond tothese results, and careful pyrometer readings should be taken for thispurpose. I have also found it important to keep the percentage ofelements, such as carbon and manganese, which are not used for thepurpose of my invention as low as possible-say carbon under about .12per cent. and manganese under about .12 per cent. This, of course, is tobe understood as a statement of conditions to be observed when the bestresults are desired.

It will be seen that by myinvention a certain proportion of pure iron isreplaced with a body such as silicon, aluminium, or phosphorus, whichare materials of low magnetic properties or so-called non-magneticmaterials. This addition has a very remarkable efiect on the magneticpermeability, the elec trical resistance, and the hysteresis quality ofthe alloy produced. In fact, the improved alloy has a higher magneticpermeability and a lower hysteretic constant than any magnetic body ofwhich I could obtain data, including the purest iron I could obtain.This remarkable result may be due to the strong chemical affinities ofthe aluminium, silicon, or phosphorous for oxygen and the halogens.Whatever the reason of the superiority of my alloy may be, the fact ofthis superiority has been well established and in itself furnishes atest for the identification of the magnetic body made according to myinvention.

I desire it to be understood that aluminium and phosphorus and theircombinations with each other or with silicon are to be consideredequivalents of silicon for the purposes of my invention,-as well as anyother element or combination of elements which will produce the sameresult-to wit, a greater magnetic permeability, a higher electricalresistance, and a lower hysteresis quality than is exhibited by thepurest commercial iron obtainable. The claims as hereunto appended whilementioning only silicon are to be understood as covering theseequivalents.

I claim as my invention- 1. A magnetic material containing a magneticbody'with an admixture of silicon in such proportions as to increase themagnetic permeability and electrical resistance and to decrease thehysteresis quality of the material to figures above and belowrespectively those which obtain with the purest iron commerciallyobtainable.

2. A magnetic material containing iron with from one to five per cent.of silicon and showing a magnetic permeability and an electricalresistance higher, and a hysteresis in alloying a magnetic body withsilicon,

heating the alloy to a relatively high temperature below itsmelting-point, allowing the alloy to cool, reheating it to a temperaturebelow that first employed, and allowing it to cool slowly.

5. The herein-described process of producing a magnetic material of highpermeability and low hysteresis action which consists in alloying amagnetic body with from one to five per cent. of silicon, heating theresulting mixture to a relatively high temperature below itsmelting-point, allowing it to cool, reheating it to a temperature belowthat first employed, and then allowing it to cool slowly.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ROBERT A. HADFIELD.

Witnesses:

JOHN LOTKA, HANS v. BRIEsEN.

